The Study On Modification Of LCO Cathode Material For Lithium-Ion Battery

Currently the main application field of LiCoO₂ is the traditional 3C electronic products.In order to release higher energy in a smaller space,the next development direction for LiCoO₂ is high voltage and high tap density,which can take off more lithium ions from the crystal structure and the specific capacity can be up to reach about 180 mA?h/g.In this paper,LiCoO₂ cathode material was prepared by solid-state ball milling-sintering method.As well,the crystal structure,morphologies and electrochemical properties of the material were characterized by XRD,SEM,electrochemical workstation and LAND test system.Firstly,the LiCoO₂ cathode material precursor with controlled particle size was prepared by solid-state ball milling,and then the LiCoO₂ cathode material was obtained by two-step sintering.Here,the effects of the lithium-cobalt molar ratio,pre-calcination temperature,and the corresponding time,and final calcination temperature and the corresponding time on the structure,morphology and electrochemical properties of the material were investigated.Finally,LiCoO₂ cathode material was obtained at an optimized condition and the proceed was as follows:1?The optimal preparation method was as follows:LiCoO₂ precursor was prepared by solid-phase ball milling with tricobalt tetroxide and lithium carbonate as raw materials and ethanol as dispersant,and then the LiCoO₂ cathode material was prepared by a two-step sintering method in a muffle furnace under an air atmosphere.In this process,the optimum molar ratio of Lithium and cobalt was 1.05:1,the first calcination temperature set up at 400oC and held for 10 h.After grinding through 200mesh sieve,the calcination temperature was further up to 850oC and kept for 8 h.The obtained LiCoO₂ cathode material was characterized by XRD and SEM.The obtained LiCoO₂ cathode material with the optimized conditions showed good electrochemical performance.At the current density of 0.1 C,the first cycle charge and discharge capacity was 192.0 mA?h/g and 177.3 mA?h/g respectively,and the corresponding coulombic efficiency was 92.4%.After 50 cycles the discharge capacity was160.9 mA?h/g and the capacity retention rate was 90.8%.2?The LCO cathode material prepared under the optimal conditions was modified by LPAN coating.It was found that the physical and chemical properties of LCO cathode material were the best after adding 10%LPAN followed with twice sintering at 700oC.The first cycle charge and discharge capacity was 221.6 mA?h/g and 181.5 mA?h/g respectively,and the coulombic efficiency was 81.9%.After 50cycles,the discharge specific capacity was 163.1 mA?h/g,and the capacity retention was 89.9%,which delivered a good cycle stability.3?In the rate performance test,compared with the LiCoO₂ cathode material without LPAN coating,the LiCoO₂ cathode material with 10%-LPAN coating can still showed an excellent specific discharge capacity at high rate condition.At the current density of 0.1 C,the first cycle discharge capacity was 183.2 mA?h/g,at the current density of 2 C,the specific discharge capacity was 115.8 mA?h/g,when the current density back to 0.1 C,the specific discharge capacity was 167.9 mA?h/g,the capacity retention was 90.3%.In a summary,a protective layer formed for the LPAN coating cathode between the material and the electrolyte under a high current,which can avoid the decomposition of the electrolyte to destroy material structure and further improve the lithium ion mobility.Mntioned above synergistic effect can effectively enhance the electrochemical properties of the LiCoO₂ cathode material.